The aim of the proposed research is to study and reduce the variable use of a costly technologic procedure: colonoscopy. At $500-1000 per procedure, colonoscopy is used in screening to identify and remove adenomatous polyps or "early" colon cancer; when polyps are found, it is used in repeated surveillance thereafter. Despite controversy about the justification, national organizations, such as the American Cancer Society, have advocated aggressive use of colonoscopy in screening and surveillance. If carried out, the aggressive guidelines could lead to about 6 million colonoscopies yearly in the U.S., costing 3.0-6.0 billion dollars. We believe that variability in clinicians; utilization of colonoscopy arises from scientific uncertainties about the carcinogenic risk of polyps, the magnitude of the threat of "early" colon cancer, and the efficacy of colonoscopy and other screening procedures. An important additional problem, however, is personal anxiety. The fear of malpractice lawsuits leads to defensive clinical practice, with the technology used inappropriately to avoid "missing" and early cancer or polyp, and with the subsequent increase in costs, hazards of colon perforation, and iatrogenically induced "cancerophobia". Fearful about colostomy or other cancer consequences, patients seek and accept the hazardous, expensive technologic procedures. The research is intended to reduce the scientific confusion and the motivating anxieties. Special studies are aimed at: quantifying the malignant risk of polyps and colon cancer; evaluating the prophylactic efficacy of colonoscopy; developing targeted strategies for low-risk and high-risk subgroups; assessing low-cost alternatives to colonoscopy; and showing the disparity between anxious personal overestimates and the true legal and clinical risks. In addition to decision-analytic modelling, reviews of literature, and use of archival data bases, the research methods will include innovative case-control studies, direct examination of clinical practices by Connecticut gastroenterologists, realistic assessments of malpractice hazards, new instruments for appraising the motivating perceptions of patients and physicians, and new classifications of important clinical data that have hitherto been unanalyzed. In appropriate colonoscopy will be reduced with subsequent interventions that suitably educate patients and clinicians, monitor the reduced usage, and persuade prominent professional organizations to change guidelines or issue new recommendations.